In production of a motor to be mounted on a vehicle, taking into account unbalance which is generated in a rotor of the motor when a load on the motor is, for example, a pump having an eccentric cam portion, disk-shaped balancers each having an eccentric portion away from a rotary center may be mounted on opposite sides of an armature core respectively. Both balancers are mounted on the outer periphery of a rotor shaft such that the centers of both balancers and a center of the rotor shaft are substantially contained in one plane. Mounting the balancers on opposite sides of the armature core, the rotational unbalance generated by the eccentric cam portion of the pump can be offset.
Conventionally, however, when coils are wound around the armature core, to the opposite sides of which the balancers are mounted, the coils are wound from optional slots of the armature core, and in the case that windings of the coils are started from such slots that the wires become in contact with the eccentric portions of the balancers, the coils are bulged outwardly by the eccentric portions of the balancers. Thus, as the coil wires continue to be wound in this state, they grow into portions being in contact with the outer peripheries of the balancers and portions being not in contact with them, and therefore, an unbalance mass is generated by the coil winding.
It is an object of the present invention to provide a method of winding an armature coil, which is capable of preventing an unbalance mass being produced by the coil winding.